The invention relates to a detergent composition for machine dishwashing.
In recent years there has been an ever increasing trend towards safer and environmentally friendly detergent compositions. This has led to development of alternative complexing agents (builders), which are used instead of predominantly phosphorous based builders. Phosphate builders can be connected with eutrophication issues.
On the other hand phosphates can bind calcium and magnesium ions, can act as alkalinity source for the detergent, they are used to buffer the wash liquor in a dishwasher above pH 9 together with other chemicals such as disilicate, metasilicates and soda.
Phosphates are also able to disperse existing calcium carbonate in the wash liquor to prevent spotting on glasses.
Thus, replacing phosphates in a detergent means to compensate at least four different functions in an alkaline detergent. (1) providing alkalinity; (2) buffering capacity, (3) complexing of magnesium and calcium ions; and (4) dispersing capacity of calcium carbonate
The use of more environmentally friendly biodegradable complexing agents, such as β-alaninediacetic acid (β-ADA) and isoserinediacetic acid (ISDA) in detergents is disclosed in DE-A-3,829,847 and DE-A-4,036,995.
However, these compounds have low complexing action and only a poor replacement for the conventional builders in the finished composition.
Other documents disclosing the use of biodegradable builders in detergent compositions include EP-A-550,087 which discloses a biodegradable oxydisuccinate builder in detergent compositions and WO 97/23450 which discloses biodegradable cysteic monosuccinic acid builder in detergent compositions. JP2000063894 and JP2001003089 disclose glutamic diacetic acid builder in detergent compositions. U.S. Pat. No. 4,132,735 discloses detergent compositions comprising biodegradable acrylate polymer builders.
One other environmentally friendly builder that has been used in dishwasher detergent formulations are salts of citric acid. This has the advantage that these salts are biodegradable, and environmentally friendly. However, the builder performance of citric acid salts is far inferior to that of phosphorus based builders. Additionally this poor performance is even further compromised with increasing temperature: salts of citric acid display especially poor activity above 45° C.
Indeed the dishwasher detergents proposed to date which use environmentally friendly complexing agents have the disadvantage that they are only effective at a relatively high pH. In order to provide this high pH, pH adjusting agents usually need to be added to the composition. These pH adjusting agents can act as additional buffering system, but cause side problems of filming and spotting on dishes. Repeated wash cycles can also lead to glass and machine corrosion, and lime-scale build-up, even on dishes.
It is an object of the invention to obviate/mitigate the issues outlined above and/or to offer detergent compositions with usage and/or environmental benefits.
According to the present invention there is provided a dishwasher detergent composition comprising a strong biodegradable builder.